(a) Field of the Invention
The present invention relates to a graphene-ceramic hybrid coating layer and a method for preparing the same.
(b) Description of the Related Art
Graphene oxide (or graphite oxide, hereinafter GO) is a sheet-shaped carbon material prepared by acid treating graphite, and has a large amount of a hydrophilic functional group, a carboxyl group (—COOH), a hydroxyl group (—OH), and the like on the surface. The surface oxidizing groups produced through an acid treatment process naturally produce hydrogen-bonds with H2O. Thus, GO is generally prepared in a form of a hydration or in a water-containing slurry state, with the solid concentration of the slurry generally being about 2 to 8 wt % as long as it is not specifically treated.
When the GO is appropriately included in a film or a structure, strength thereof may be improved and suitable thermal conductivity may be provided. However, treatment of the contained moisture may hinder properties.
In general, GO may be prepared in a form of graphene through a chemical reduction method (a hydrazine treatment and the like) and a thermal reduction method. Herein, reduced graphene is particularly referred to as reduced graphene oxide (RGO).
Evidence shows that not all of the oxidizing groups on the RGO are thoroughly removed. Generally, oxygen content of the surface oxidizing groups is less than or equal to about 5% relative to a carbon backbone.
A heterogeneous mixture of RGO and a conventional material has recently evoked active interest, due to its potential to improve synergic effects between materials exceeding that of conventional materials. The heterogeneous mixture may be used in a high strength composite material and a fuel cell. As representative technologies, Korean Patent No. KR2011-0012479 describes a graphene-nanowire (semiconductor) hybrid structure where light energy is absorbed in a graphene conductive part and electron-hole pairs are generated. Korean Patent No. KR2010-0114646 describes a hybrid composite manufacturing method including graphene sheet/carbon nanotube/a polymer nanoparticle. Korean Patent No. KR2010-0097322 describes a method of manufacturing a positive electrode graphene material for a lithium rechargeable battery that is a hybrid material formed by adding an Fe precursor and a PO4 precursor. U.S. Pat. No. 8,257,867 describes a method of manufacturing a graphene composite calcinated body having an excellent charge and discharge ratio by sintering graphene and a metal oxide particle in air. U.S. Patent Publication No. 2012-0149554 describes a method of manufacturing a graphene-TiO2 hybrid material by mixing a TiO2 nanopowder with graphene at a high temperature and high pressure and reacting them.
However, improved materials are still needed.